Multi-method approach to dating glass: The case of Basiluzzo Islet (Aeolian archipelago,Italy)

A rhyolitic lava flow from Basiluzzo islet (Aeolian Islands), has been analysed with the Fission tracks (FT) and ⁴⁰Ar–³⁹Ar methods on glass, and with the U/Th method on whole rock to constrain its age and to compare the behaviour of different dating methodologies on glass samples late Quaternary in age. Laser ⁴⁰Ar–³⁹Ar total fusion analyses were performed on populations of grains. Due to the low yields of radiogenic ⁴⁰Ar the age data are characterised by very high errors. The weighted average of the ages of the whole population is 55.7 ± 8.7 ka (MSWD = 0.7). The isochron age calculated on all points is 40.6 ± 11.4 ka (MSWD = 0.6), with an initial ⁴⁰Ar/³⁶Ar ratio of 297.8 ± 1.8; the isochron is characterised by very little spread among points. The procedure named ‘point-counting technique’ was adopted in FT dating. Spontaneous track mean size resulted reduced by around 20% compared to induced tracks, which indicates that the determined FT age, 28.6 ± 3.6 ka, is a reduced age, due to a certain amount of track annealing. For this reason the plateau technique for correcting thermally lowered ages was applied. We determined a plateau age (commonly assumed as a reliable estimate of the glass formation age) of 43.4 ± 7.1 ka. Four sub-samples of whole rock from Basiluzzo lava flow have been analysed using U/Th isochron method. The ²³⁸U/²³²Th and ²³⁰Th/²³²Th activity ratios of sub-samples have been determined by alpha counting and plotted on an isochron diagram. The resulting age is 46 ± 8 ka and the ²³⁴U/²³⁸U activity ratios are always close to one, demonstrating that no significant processes of alteration have occurred. The relatively high error associated with the age is due to a low fractionation of U/Th ratio in the analysed whole rocks. The ages obtained with different methods, 43.4 ± 7.1 ka (FT plateau age), 40.6 ± 11.4 ka (⁴⁰Ar–³⁹Ar isochron age of all grains), and 46 ± 8 ka (U/Th isochron) agree at the 1σ level, excluding a Holocene age for this sample. This could be valuable information for the Department of Civil Protection because it seems to mitigate the potential risk for present volcanic activity in the area. All ages are affected by very high analytical errors, which are due to the characteristics of the material analysed. Young ages result in low tracks numbers (FT dating) and barely detectable amounts of radiogenic ⁴⁰Ar in the presence of high atmospheric contamination (⁴⁰Ar–³⁹Ar dating). Stratigraphic successions without strict chronologic constraints might however benefit even from age data with low precision.     

Uranium and thorium isotopes in minerals from the « Cetara — Serrara Fontana » tuff (Ischia Island,Italy) — A tentative radiometric dating

A cineritic level, which appears very interesting from a chronostratigraphic point of view because it is found throughout the eastern Mediterranean Sea, has been related to the « Cetara — Serrara Fontana » tuff formation (Ischia Island, Italy) by previous authors who estimated the age of this cineritic level to be about 25,000 years. A direct dating of the « Cetara — Serrara Fontana » tuff has been attempted by means of isotopic analyses of uranium and thorium in sphene, glass, clinopyroxenes and magnetite from four tuff samples. The calculated age is 41,500±3,000 years only if glass and sphene are assumed to be coeval. On the other hand, assuming as true the age of 25,000 years for the Cetara tuff, we must conclude that the sphene crystallized before the eruption. The age of the clinopyroxenes and magnetite is older than 300,000 years: therefore, they are possibly pre-existing minerals reworked by the Cetara explosion.     

OSL dating of sediments from deserts in northern China

Aeolian samples from deserts in northern China were studied using the optically stimulated luminescence (OSL) of quartz and potassium (K) feldspar separates. K-feldspar has shown advantages over quartz for dating samples younger than 100 years, due to its more homogeneous equivalent dose (D_e) values, higher internal dose rate and higher luminescence sensitivity to dose. Without additional measurements, the luminescence characteristics of quartz obtained in D_e determination procedures can be used to reveal the source material and/or quartz thermal history for the deserts in northern China. The results indicated that the duration of paleosol formation in desert areas reflects regional paleoenvironments.     

Paleomagnetic stratigraphy and radiometric dating of the pliocene volcanic rocks of Aegina,Greece

The island of Aegma includes some of the oldest volcanic rocks in the south Hellenic Arc previous radiometric dates range from 3.87 to 4.4 Ma. The volcanic sequence is divided into nine units on the basis of field relations, petrography and geochemistry, and the characteristic paleomagnetic polarity of each unit has been determined. Two new radiometric dates (2.1 and 3.9 Ma) show that the volcanism spans the Pliocene. A detailed chronology is proposed using the paleomagnetic data which places the most voluminous volcanism in the mid Pliocene.     

Age of glacial and periglacial landforms in northern Hokkaido, Japan, using OSL dating of fine grain quartz

The timing of glacial advances, periglacial phenomena, and the ages of two marker tephras in northern Hokkaido were estimated by OSL dating. It appears that the glacier of Yamunai 2 stage on Rishiri Island expanded between 24 and 15 ka. In northern Hokkaido, OSL ages indicate ice wedge formation during the period 24–18 ka. These results indicate that both the glacial advance and the development of ice wedges were synchronous phenomena relating to the Last Glacial Maximum.     

Middle and early cretaceous magnetic stratigraphy from the Cismon section,northern Italy

The pelagic limestones exposed in the valley of the Cismon river (near Feltre) appear to represent continuous deposition from Valanginian to Campanian, apart from a short hiatus in the Early Albian. Detrital magnetite is the carrier of remanence in these predominantly white-grey limestones, and a well-defined magnetic stratigraphy has been obtained. The Cretaceous quiet zone at Cismon is totally normal in polarity and stretches from Early Aptian to Early Campanian. Below the Lower Aptian, the Early Cretaceous mixed polarity interval is tentatively correlated with the sequence of geomagnetic reversals derived from the oceanic magnetic anomalies.     

冀北承德盆地早白垩世火山-沉积地层地质年代学研究: 对热河生物群时空演化的制约

热河生物群是世界闻名的陆相生物化石宝库, 保存了大量特异埋藏化石, 为研究早白垩世脊椎动物、昆虫和植物的演化提供了绝佳的素材.依据古生物组合的不同, 将其分为早、中、晚三期, 分别赋存于河北丰宁花吉营组、辽西义县组和九佛堂组及其周边地区相当层位.河北承德—围场地区处于早-中期热河生物群分布地区的过渡地带, 近年来不断的化石发现为研究华北克拉通破坏及其对陆地生态系统的影响提供了关键证据.但由于缺乏准确的年龄约束, 对于含化石层位的准确时代及其与邻区地层对比存在较大争议.本文利用来自于河北北部承德盆地袁家庄剖面的3个安山岩样品的锆石, 进行化学熔蚀-离子探针(CA-SIMS)锆石U-Pb定年, 获得年龄为129.6~128.7 Ma.结合前人发表的磁性地层学结果建立了新的磁性地层学对比方案和新的综合年代框架, 揭示了该剖面火山-沉积序列记录了古地磁极性序列M8n-M7n, 进一步证明了袁家庄剖面的陆相火山-沉积层序属于欧特里夫晚期.结合区域内前人年代学结果, 将该区域热河生物群化石层时代限定为130~127 Ma.年代地层学对比结果显示, 承德盆地早白垩世火山-沉积序列与滦平盆地大店子组和森吉图—四岔口盆地花吉营组上部时代相当, 明显老于辽西义县组时代, 揭示了华北克拉通北缘早白垩世陆相地层的自西向东逐渐年轻的特征.

     

DRAC: Dose Rate and Age Calculator for trapped charge dating

Accurate calculation of the environmental radiation dose rate (Ḋ) is an essential part of trapped charge dating methods, such as luminescence and electron spin resonance dating. Although the calculation of Ḋ is not mathematically complex, the incorporation of multiple variables and the propagation of uncertainties can be challenging. The Dose Rate and Age Calculator (DRAC) is an open access, web-based program which enables rapid Ḋ calculation for trapped charge dating applications. Users can select from recently published attenuation and conversion factors to make mathematically robust, reproducible Ḋ calculations. Comparison of DRAC calculated Ḋ values against the published Ḋ determinations of 422 samples from 32 studies results in a reproducibility ratio of 1.01 ± 0.05. It is anticipated that DRAC will facilitate easier inter-laboratory comparisons and will provide greater transparency for Ḋ calculations. DRAC will be updated to reflect the latest advances in Ḋ calculation and is freely accessible at www.aber.ac.uk/alrl/drac. The code for DRAC is available from github at https://github.com/DRAC-calculator/DRAC-calculator.     

Multi-method pIRIR dating of sedimentary sequences at the southern edge of the Gurbantunggut Desert,NW China and its palaeoenvironmental implications

The Gurbantunggut Desert is the second-largest desert in China, located in the westerly-dominated region of north-western China. Previous understanding of palaeoclimate of this desert was mostly based on lake and loess records from the Junggar Basin and Tian Shan Mountains, whilst direct dating of sedimentary records from the desert was very limited. This study applies high-resolution post-infrared infrared stimulated luminescence (pIRIR) dating to three sedimentary profiles at the southern edge of the Gurbantunggut Desert, which contain aeolian sand and water-lain sediments, recording palaeoenvironmental changes at the desert margin since the Last Glacial Maximum (LGM). Different pIRIR dating procedures were applied for samples with different ages. For Holocene-aged samples, a single-aliquot regenerative-dose (SAR) pIRIR procedure based on a three-stepped pIRIR measurement at 110 °C, 140 °C and 170 °C was used, and a standard growth curve (SGC) procedure yields an equivalent dose (D_e) similar to that of the full-SAR procedure; thus, is applicable for accelerating D_e measurement. For samples much older than the Holocene, a multi-aliquot regenerative-dose (MAR) pIRIR procedure based on a three-stepped pIRIR measurement at 150 °C, 200 °C and 250 °C was found to be the optimal dating procedure, because a SAR procedure would yield underestimated ages due to uncorrected initial sensitivity change. pIRIR dating results of the investigated profiles reveal a substantial sand accumulation during the LGM, an intensification of aeolian deposition at ∼12 ka and a wetter depositional environment at ∼10–8 ka. A rapid fluvial deposition is dated at ∼20–19 ka, corresponding to the deglaciation period. The sedimentary records from the desert margin show some correlation with lake and loess records in the same region and suggest a complex response of the desert environment to different climatic factors.     

Oxygen and hydrogen isotopes in the volcano-sedimentary complex of Huelva (Iberian Pyrite Belt): example of water circulation through a volcano-sedimentary sequence

The minerals of basic and acidic rocks from the volcano-sedimentary sequence in the Huelva area, Spain, Iberian Pyrite Belt, display an extendedδ¹⁸O enrichment. Quartzδ¹⁸O values from quartz-keratophyres vary from +10.5 to +17.0 and feldsparδ¹⁸O values from +14.4 to +16.0. For the spilite or spilitized doleritesδ¹⁸O values vary from +9.9 to +13.4 for feldspar, from +6.4 to +9.8 for chlorite, from +3.7 to +4.3 for ilmenite and from +13.6 to +14.0 for quartz, but pyroxene exhibits magmatic values, from +5.3 to +6.1 with an exception at +7.5. The chloriteδD values vary from −34 to −43‰.This is attributed to hydrothermal alteration with seawater enriched inδ¹⁸O by circulation through sediments.The temperatures of interaction determined from isotopic fractionations between minerals range from 400° to 520°C.CalculatedδD andδ¹⁸O values for water in equilibrium with the minerals at isotopic temperatures range from −16 to +5 and from +8.3 to +12.8, respectively.A model of circulation of seawater through a pile of sedimentary rocks and then through basaltic rocks is proposed to explain the high¹⁸O compositions of the rocks from the Huelva District. Water/rock mass ratios calculated from this model range between 0.3 and 0.7 for the determined range of temperatures.     

Transferring radiometric dating of the last interglacial sea level high stand to marine and ice core records

In order to derive a radiometric age marker for the end of the penultimate glacial–interglacial transition, we compiled published U-series isotope measurements on corals from the period extending from stage 6 to the middle of the last interglacial, and computed the corresponding open-system ages using Thompson et al. model (Thompson, W.G., Spiegelman, M.W., Goldstein, S.L., Speed, R.C., An open-system model for U-series age determinations of fossil corals. Earth Planet. Sci. Lett. 210 (2003) 365–381). We obtain a global mean age of 126 calendar kyr BP (ka) ± 1.7kyr (2σ) for the beginning of the last interglacial sea level high stand. After showing that the phase relationships observed between changes in sea level, North Atlantic benthic and planktonic foraminifera oxygen isotopic records, and atmospheric methane over the last deglaciation were likely also valid over the penultimate deglaciation, we derive an age of 131.2ka ± 2kyr (2σ) for the abrupt increase in atmospheric CH₄ and North Atlantic surface temperature marking the end of the penultimate glacial–interglacial transition. This age is consistent with U–Th dates of the penultimate glacial–interglacial transition recorded in speleothems from sites where speleothems isotopic records are synchronous with North Atlantic temperature records over the last deglaciation. Finally, we show that the phase obtained between the climatic response and northern hemisphere summer insolation is not constant from Termination II to Termination I, implying that northern hemisphere summer insolation alone cannot explain the timing of terminations.     

Underestimation of fine grain quartz OSL dating towards the Eemian: Comparison with palynostratigraphy from Azzano Decimo,northeastern Italy

Palynostratigraphical records have been used to understand the response of vegetation to climate change, and benefit from independent dating to ensure a robust correlation with global climate and sea-level change. In order to constrain the pollen chronology of a long sedimentary core taken at Azzano Decimo in the Friulian foreland of northeastern Italy, optically stimulated luminescence (OSL) has been applied to fine grain quartz. The samples meet all the standard performance criteria set to test the reliability of the single-aliquot regenerative-dose (SAR) protocol, and still show increasing dose response at 500 Gy. OSL ages are in good agreement with radiocarbon dating and the pollen interpretation down to 70 ka, and with D_e values of ～140 Gy, but below this point, they display an increasing age underestimation towards the Eemian and beyond. The comparison of D_e values measured using both a SAR and single-aliquot regeneration and added-dose (SARA) protocol, confirmed that both were successfully correcting for sensitivity changes in the quartz during measurement of the burial dose, and this was not the reason for the age underestimation. The quartz OSL dose response curve for all samples is best described by a saturating exponential plus linear (SEPL) function. Although all underestimated ages are derived from D_e values that fall on the high dose linear region of this curve, it is unclear if this is the cause of the underestimation.     

Age and duration of the réunion geomagnetic polarity event

Palaeomagnetic studis on oriented samples from two sequences of olivine basalt lava flows on the island of Réunion together record the Réunion normal polarity event within the Matuyama reversed polarity epoch. Detailed K?Ar dating of the lavas indicates that the Réunion event has a mean age 2.02±0.02 my with a duration estimated to lie within the range 10,000 to 50,000 yr. This could explain the rarity of detection of the event in deep sea sedimentary cores.     

ReOSL dating of aeolian and fluvial sediments from Nihewan Basin,northern China and its environmental application

The Nihewan Formation, consisting of thick fluvio–lacustrine sediments with abundant mammalian faunas and Paleolithic remains, is widely distributed in the Nihewan Basin, northern Hebei Province, China. In this study the fluvio–lacustrine sediments of the Nihewan Formation and the loess–paleosol sequence evident in the Haojiatai Section were dated by recuperated OSL (ReOSL) of fine-grained quartz (Wang, X.L., Lu, Y.C., Wintle, A.G., 2006a. Recuperated OSL dating of fine-grained quartz in Chinese loess. Quaternary Geochronology 1, 89–100.). The preliminary ReOSL dating results show that: (i) the loess–paleosol sequence in the upper part of the profile started to develop at about 128 ka ago; (ii) the unconformity separating the loess–paleosol from the underlying Nihewan Formation represents a sedimentation break of about 130 ka. On the basis of the ReOSL dates and related stratigraphic evidence it is proposed that the ancient Lake Nihewan dried shortly after about 266 ka.     

First archaeomagnetic results and dating of Neolithic structures in northern Greece

Archaeomagnetism in Greece has continuously developed during the last decades. Numerous studies have provided high quality data and accurate secular variation curves for the direction and intensity of the geomagnetic field have been constructed. The Greek Secular Variation Curves (SVCs) cover the last 8 millennia for intensity and 6 millennia for direction. The coverage of the archaeological periods remains uneven, with several gaps, mostly in the directional dataset, with only two results for periods older than 2500 B.C. In the present contribution, the first archaeomagnetic results from Neolithic settlements in northern Greece are presented. For the present study, samples were collected from three different archaeological sites: burnt structures in Avgi (Kastoria) and Vasili (Farsala) and one oven from Sosandra (Aridaia). The natural remanent magnetization (NRM) grouping of all specimens indicated that the majority of the samples were burnt in situ, providing thus a reliable direction of the ancient field. Magnetic cleaning (both alternating-field and thermal) revealed the presence of one stable component of magnetisation. Rock magnetic experiments (acquisition of isothermal remanent magnetization (IRM), thermal demagnetisation of the IRM, thermomagnetic curves) have been performed on pilot samples indicating that low coercivity magnetic minerals such as magnetite or Timagnetite are prevailing. The mean directions (declination D, inclination I and parameters of the Fisherian statistics), which arose from the three sites are as follows: Sosandra: D = 343°, I = 55.6°, ??₉₅ = 4.8°; Avgi: D = 10.1°, I = 53.4°, ??₉₅ = 4.2° and Vasili: D = 357.5°, I = 43.1°, ??₉₅ = 4.1°. The obtained data are in a very good agreement with results from Neolithic Bulgaria. This study represents the beginning of an effort to fill the gaps of the Greek secular variation curves and their extension to the Neolithic period.     

Palaeomagnetic and palaeontological dating of a section at Gioia Tauro,Italy: Identification of the Blake Event

Palaeomagnetic and palaeontological studies on samples withdrawn from a 250-m-long unorientated core from Reggio di Calabria, Italy (38°N, 16°E) are described. The lower 200 m of core penetrated off-shore clays and visual examination of the split sections of core indicated no obvious breaks in deposition. After alternating field demagnetization in 200 Oe the palaeomagnetic inclination log shows the Brunhes/Matuyama boundary at 110 m below which the Jaramillo and Olduvai Events within the Matuyama Epoch are identified. This interpretation of the magnetostratigraphy is supported by palaeontological evidence. The rate of accumulation of clay is estimated to have ranged between about 60 and 190 mm/kyr with an overall average through the Matuyama Epoch of about 90 mm/kyr. Assuming that this average rate continued through the Brunhes Epoch, the age of the top of the clay unit is estimated to be about 90,000 yr B.P. About 5 m from the unconformable top surface of the clay, a split sequence of reversed inclinations is interpreted as a record of the Blake Event, and the overall average deposition rate implies that its duration may have been as long as 50,000 yr. No other reversed event is recorded by the palaeomagnetic inclination log through the Brunhes Epoch, though there are four horizons where shallow positive inclinations are recorded.     

Age of New Zealand Pleistocene substages by fission-track dating of glass shards from tephra horizons

Eleven tephras and two pumice-rich horizons interbedded in Pleistocene marine sediments of the Wanganui Basin have been dated using the fission-track method on glass shards. Ages of the lower boundaries of New Zealand Pleistocene marine Substages are 0.45 m.y. (Putikian), 1.06 m.y. (Okehuan), 1.55 m.y. (Marahauan). On the basis of sedimentation rates an estimation of 1.86 m.y. is obtained for the Plio-Pleistocene boundary (Hautawan).     

Strong-motion observations from the OGS temporary seismic network during the 2012 Emilia sequence in northern Italy

Strong-motion data consisting of peak ground acceleration and velocity and 5 % damped response spectra are presented for 46 earthquakes of the Emilia seismic sequence which occurred in the Po Plain (northern Italy) in 2012. The data were recorded by the OGS temporary network installed close to the town of Ferrara following the main shock of May 20, 2012. Ground-motion peak parameters and spectral responses are compared with the ground-motion prediction equation (GMPE) of Bindi et al. (Bull Earthq Eng 9:1899–1920, 2011) for soft soils and reverse faults. Peak ground accelerations are in general in good agreement with those predicted by GMPE, while predicted peak ground velocities underestimate the observed data, especially for stronger events at more distant stations. The response spectra follow the trend in peak ground velocities, with observed values higher than predicted values at longer periods. This behavior has been interpreted as a site effect due to the deep soft alluvial cover of the Po Plain, which promotes ground motion characterized by a large low-frequency spectral content that is not yet well modeled by the Italian GMPE. A peculiar behavior was shown by the event occurring on June 6, 04:08:33 UTC, \(\hbox {M}=4.5\) , located at the eastern edge of the Po Plain, which produced peak ground accelerations exceeding three times the values estimated by attenuation laws. Such a great discrepancy could be related to post-critically reflected S-waves and multiples from the Moho (SmSM).     

Optical dating of the upper 22 m of cored sediments from Daihai Lake,northern China

Daihai Lake is one of the largest lakes in the mid-latitude of northern China. Previous environmental change investigations using the sediments from the lake have been mainly focused on the last 13 ka. In 2006, we drilled an 80-m borehole on the southwest coast of the lake. Here we report the results of initial optical dating of the upper 22-m sediments from the core. Most of the samples allow separation of the 4–11 μm fine-grained and 45–63 μm medium-grained quartz, both of which were used for equivalent dose (D_e) determination. Dose recovery test experiments with the single-aliquot regeneration-dose (SAR) protocol indicate that a preheat at 240 °C for 10 s combined with a cut-heat of 240 °C is suitable for these samples. The D_e values show marked discrepancy between the two grain size fractions with the fine-grained quartz yielding up to over 50% higher D_e values than the medium ones for some samples. We consider the OSL ages for the samples from upper ～10 m to be overestimated. The main cause of the overestimation is attributed to the incomplete bleaching of the sediment grains at deposition. The OSL ages for the lower part of the sequence are considered to be reasonable age estimates which provide useful temporal constrains on the deposition of the sediments for the period of 20–40 ka.     

A strong motion network in northern Italy: detection capabilities and first analysis

The necessity of a dense network in Northern Italy started from the lack of available data after the occurrence of the 24th November 2004, Ml 5.2, Salò earthquake. Since 2006, many efforts have been made by the INGV (Italian National Institute for Geophysic and Vulcanology), Department of Milano-Pavia (hereinafter INGV MI-PV), to improve the strong-motion monitoring of the Northern Italy regions. This activity led to the installation of a strong-motion network composed by 20 accelerometers, 4 coupled with 20-bits Lennartz Mars88 recorders, 12 coupled with 24-bits Reftek 130 recorders and 4 coupled with 24-bits Gaia2 recorders. The network allow us to reduce, in the area under study, the average inter-distances between strong-motion stations from about 40 km (at November 2004) to 15 km. At present the network includes nine 6-channels stations where velocity sensors work together the strong-motion ones. The data transmission is assured by modem-gsm, with the exception of four stations that send data in real time through a TCP/IP protocol. In order to evaluate different site responses, the stations have been installed both in free field and near (or inside) public buildings, located in the center of small villages. From June 2006 to December 2008 a dataset of 94 events with local magnitude range from 0.7 to 5.1 has been collected. An ad hoc data-processing system have been created in order to provide, after each recorded event, engineering parameters such as peak ground acceleration (PGA) and velocity (PGV), response spectra (SA and PSV), Arias and Housner intensities. Data dissemination is achieved through the web site , while the waveforms are distributed through the Italian strong motion database ().